Authentication of the identity of a user of a computing device, or a user that wants to access a proprietary data item, software application or on-line service, is important to prevent an unauthorized person from masquerading as an authorized user. This type of identity theft can have devastating results such as loss of secure information, theft of products or services, and so on.
Current authentication schemes for ensuring the authenticity of a user typically require a password from the user at the start of each session or after a period of inactivity. Some schemes wait a fixed amount of time before requiring re-authentication, which typically entails the user re-entering a password after this fixed amount of time elapses.